1. Field of the Invention
The present invention relates to a golf club head for a putter and a golf putter.
2. Description of the Related Art
Putting is performed aiming at rolling of a golf ball on the surface of earth (principally on the green), and involves characteristics that are different from other shots aiming at flying of the ball.
Although it is difficult to identify visually, behavior of the ball immediately after hitting by a putter differs variously. Undesired behavior of the ball immediately after hitting by the putter may be back spin and bound.
In some cases, back spin may be applied to the ball immediately after hitting by the putter. While the back spin is applied, the ball does not move as it rolls on the surface of earth but moves as it slips. This back spin is ceased after a while due to the frictional force between the surface of earth and the ball. The ball after ceasing of the back spin moves as it rolls with overspin. The back spin reduces the distance of rolling of the ball. Because the back spin is accompanied by slipping, it is probable that trajectory of rolling of the ball is destabilized. Therefore, excessive back spin can be a factor to reduce the probability of getting the ball in the cup.
Also, there may be a case in which the ball hit by the putter gets away from the surface of earth for a moment through jumping, bounding or the like. While the ball is getting away from the surface of earth, the ball is not influenced by the slope of the green. Thus, the putting line in the case in which the ball gets away from the surface of earth is different from the putting line in the case in which the ball does not get away from the surface of earth. In addition, the putting line shall vary depending on the distance of the flight of the ball in the air. The difference in the putting lines may make prediction of the putting line difficult, whereby the probability of getting the ball in the cup can be reduced. The putting line means a trajectory of the ball from the position where the ball is hit to the position where the ball drops in the cup.
Therefore, for improving the probability of getting the ball in the cup, favorable rolling of the hit ball (hereinafter, may be also referred to merely as favorable rolling, or, stability of rolling) would be important. The state of favorable rolling may be a state in which the ball after hitting immediately rolls with overspin without excessive flight in the air. The favorable rolling makes prediction of the putting line easier, and increases the rolling distance. Japanese Registered Utility Model No. 3057456 discloses a golf club head for a putter which can easily apply overspin by having a loft angle generated by inclining in a direction that is reverse to general loft (hereinafter, maybe also referred to as reverse loft angle), and by setting this reverse loft angle to be 0 to 5 degree.